Just before Thanksgiving, news broke about a new stem-cell technique that could produce the equivalent of embryonic stem cells (ESCs) but without using or destroying human embryos. We referred to the news that these cells, called induced pluripotent stem cells (iPSCs), could be made from human skin cells as a Stem-Cell Breakthrough marking The End of the Stem-Cell Wars . It certainly gave us one more thing for which to be thankful when we sat down to dinner that Thursday night.
Many Americans consider research on human embryos to be fundamentally wrong. Even some who do not share this conviction are nonetheless uneasy with using human embryos as research material. James Thomson recently remarked in an interview with the New York Times , If human embryonic stem cell research does not make you at least a little bit uncomfortable, you have not thought about it enough. Good research, research that truly advances our knowledge, enhances our lives, and ennobles our culture, must respect both scientific and ethical standards. IPSC research meets the highest standards of science, and it respects the ethical standards of many Americans who object to human embryonic stem cell research as deeply immoral.
But some scientists cant fathom the idea of limits being placed upon them, and their visceral reaction has produced some commentary that is just downright bizarre. Lee Silver, a professor of biology at Princeton, suggests that the pro-lifers are fools¯and that scientists are duping them. On the one hand, he argues that there should be no ethical concerns at all, for embryos and skin cells are more or less the same. On the other hand, Silver thinks that this new technique should not relieve any pro-lifers worries, since the stem cells it produces can (he claims) develop into babies. Scientists know this, Silver says, but they are hiding it from the public in a massive propaganda campaign.
Who would promote Silvers science-cabal conspiracy theory, you ask? We found it in our inboxes in the daily New York Times e-mail. Right at the top was the link to a video interview between science writer Carl Zimmer and Lee Silver.
What Embryos Are
Silver tries to paint the ethical debate as one of enlightened science versus fundamentalist religion: Are cells just complex information-processing machines, which is the way most biochemists and molecular biologists look at cells, or is there something mystical and vitalistic about certain cells¯embryo cells?
Barely veiling his disdain, he fires a second rhetorical question: Is there something fundamentally, ontologically different about human embryo cells versus human skin cells? Claiming the mantle of science for himself, Silver answers:
As a biochemist and molecular biologist looking at it, the only fundamental difference is that there are different proteins sitting on the DNA in different places which causes these two cells¯which have the same DNA¯to look a bit different from each other, to have different potential from each other. Thats not a fundamental difference.
This characterization totally ignores the numerous other cellular factors that contribute to differences between cells, but, even granting him this rather simplistic view, his argument is ridiculous. Which proteins are sitting where¯the epigenetic state of a cell¯ is a fundamental difference. Epigenetic state is the only difference between any two cells in the body. Liver cells and brain cells do not merely look a bit different from each other, they have a profoundly different composition, function, and morphology (form), based on their epigenetic state. Moreover, the epigenetic state of a cell can make a fundamental difference, the difference between a whole and a part, an organism and a mere clump of cells. The epigenetic state of a one-celled embryo is unique in that it produces and organizes all the cells of the body.
The view¯held by almost everyone irrespective of their moral opinions¯that embryos are fundamentally different from other cells, has nothing to do with religion and everything to do with the scientific evidence. To draw any moral conclusions on how embryos should be treated¯be it from a religious or a secular ethical standpoint¯one first has to answer the question What is an embryo? Only by settling what an embryo is ¯a question of biological fact, not theological speculation¯can one determine an embryos moral status and what interest God and society might (or might not) have in protecting it or permitting it to be killed to benefit others. Our disagreement with Silver is over the scientific evidence. It has nothing to do with religion.
But of course Silvers habitual tactic is to bring peoples religious affiliations into it:
The opponents are all Jewish, mostly Christian. And they have this view that embryos are different from other kinds of cells. Very often they wont admit it, but its a vitalistic notion, meaning theres something beyond the material substance of an embryo that gives it its properties, that allows it to develop into a human being.
What does the science really say? Whereas sperm and egg are genetically and functionally parts of larger organisms, the embryo functions as a whole organism. In addition to the genome, the total epigenetic state of the zygote is such that, given a suitable environment and adequate nutrition, it will develop by an internally directed process that both generates and organizes all the components of the mature body. This is why no one is ever surprised when the human embryo matures into a human adult. Precisely because of what the embryo is now ¯namely, a living member of the human species¯we can confidently predict how it will develop and what its final (mature) stage will be. The only conclusion consistent with the scientific evidence is that the embryo is not something distinct from a human being but is rather a human being at the earliest stage of his or her natural development.
The leading works of human embryology corroborate this. The chapter on human development in Keith L. Moore and T.V.N. Persauds The Developing Human begins with this sentence: Human development begins at fertilization when a male gamete or sperm (spermatozoon) unites with a female gamete or oocyte (ovum) to form a single cell¯a zygote. This highly specialized, totipotent cell marked the beginning of each of us as a unique individual . Or their definition of embryo : The developing human during its early stages of development. And consider their definition of the term zygote : This cell results from the union of an oocyte and a sperm during fertilization. A zygote is the beginning of a new human being (i.e., an embryo) (emphasis added).
Yes, Professor Silver, respected medical textbooks do indeed use the term human being, contrary to your assertion that none of the standard texts . . . actually states that an embryo is a human being.
Living embryos are fundamentally different from mere living cells precisely because they are able to both generate and organize the cells of the body into an integrated whole owing to the unique epigenetic state of the zygote. If the capacity for organization is not a fundamental difference between cells and embryos, what basis is there for distinguishing highly organized molecular biologists from mere human cells? One could, in theory, manipulate the organization of Silvers body by dissociating it into a cellular suspension, without destroying cells or altering their epigenetic state. How could Silver possibly object to this transformation of his body into a cellular soup, since, in his view, there is no fundamental difference between human living cells and living human organisms?
Perhaps Silver would object that, in a mature state, he manifests sufficient organization to be considered fundamentally different from a cellular suspension, but that when he was in an embryonic state this was not the case. But does Silver deny that he was once an embryo? If so, on what grounds? Certainly he is the same biological organism that was once inside his mothers womb. As the embryology texts confirm, the human individual that is now Lee Silver is the same individual¯the same living member of the human species¯that came into existence when the gametes contributed by his parents joined to bring about the embryo that would develop by a gradual, gapless, and self-directed process of growth to adulthood. If Silver maintains he was never an embryo, but rather that the embryo merely gave rise to a molecular biologist at some later point, does he think that a mysterious infusion of some spiritual or other nonbiological feature worked this transformation? Perhaps Silver is the party in this debate who is secretly embracing mystical and vitalistic faith to support his nonscientific conclusion regarding the embryo.
Do Stem Cells Grow Up and Become Babies?
While Silvers claim that human embryos and human skin cells are more or less the same is bizarre, his argument that scientists are deceiving the public is down right outrageous¯and should receive condemnation from all conscientious scientists and anyone interested in honest public debate. Here is what Silver says:
The scientists are very careful about the language, so this is political science, this is not molecular science. And the political science is that were not going to call them embryonic stem cells even though the whole point is that they are embryonic stem cells. And, were not going to call them clones even though, in fact, they are clones. Were going to avoid those words, those words are contentious, and by avoiding those words everybody is going to be happy.
Thats a real fudge, because if these are really embryonic stem cells¯and they certainly look like them to me based on the data that Ive seen¯we know that the mouse version of these cells can produce a mouse and theres every reason to believe that the human version of these cells can produce a human being. But the scientists are going to make sure we dont talk about that.
This leaves two possibilities: Either Silver is correct and the scientists are trying to deceive us, in which case, how can the public ever be expected to trust them? Or Silver is wrong. Fortunately for scientists and the public, the latter possibility is the one that checks out in view of the facts. Silvers claim is total nonsense. Scientists are not engaged in a giant deception or cover-up. It is true that the iPSCs appear to have the same property of pluripotency as embryonic stem cells. But embryonic stem cells never develop into an organism on their own. They are not embryos because they lack the crucial qualities possessed by embryos by virtue of their epigenetic state. Embryonic stem cells on their own make tumors; disorganized collections of many different cell types. They make mice when they are in an embryonic mouse.
The small point Silver leaves out is that you need to start with an embryo to end up with an embryo. When embryonic stem cells are added to existing mouse embryos, they participate in normal development and contribute to the tissues of the developing mouse body. Under special circumstances (for example, tetraploid complementation or laser-assisted introduction of cells at early embryonic stages), you can manipulate the embryo in such a way that the added stem cells produce most of the tissues of the mouse body, while the cells of the manipulated embryo contribute mainly to the placenta and embryonic membranes. Nonetheless, the stem cells are not making the mouse on their own; they are merely contributing to an ongoing developmental process.
Silver confuses what something can be converted into with what it actually is. He assumes that, because a woodpile can be made into a chair, it actually is a chair, right now. Because a piece of lumber and a chair have the same DNA and (by the action of external forces) can be changed into one another, Silver concludes, they are the same thing, or at least not fundamentally different. It seems to elude Silver that a piece of wood cannot become a chair on its own, any more so than an embryonic stem cell can become an embryo on its own. In contrast, an embryo is fully and intrinsically an embryo¯a living individual of its species, a complete organism and not a mere part¯from the very beginning. Due to its unique epigenetic state, it is indeed fundamentally different from a stem cell, just as a piece of wood is fundamentally different from a chair.
Silvers belief that embryos and stem cells are not different in fundamental ways is exactly that: a personal belief, rather than a scientific position. Skin cells can be used to make embryos by cloning, and the embryonic human or other animal produced by cloning will exhibit an organized, directed pattern of development that is entirely unique to an embryo. The only conclusion that is consistent with these scientific observations is that using a skin cell to produce an embryo by cloning involves an alteration in the fundamental properties of the skin cell, by converting it from a part of an organism into a complete organism. Rather than accept a conclusion that contradicts his nonscientific beliefs about embryos, Silver simply ignores the facts and reasserts his belief that, despite overwhelming scientific evidence to the contrary, skin cells and embryos are not fundamentally different.
But, really, Professor Silver shouldnt parade his personal beliefs as scientific facts.
Ryan T. Anderson is assistant editor at First Things . A Phillips Foundation fellow, he is assistant director of the Program in Bioethics at the Witherspoon Institute of Princeton, New Jersey. Maureen L. Condic is associate professor of neurobiology and anatomy at the University of Utah and senior fellow of the Westchester Institute for Ethics & the Human Person.